#include<iostream>
#define maxn 22
long long f[maxn][maxn] = { 0 };
int d[9][2] = { {0,0},{1,2}, {1,-2},{2,1},{2,-1},{-1,2},{-1,-2},{-2,1},{-2,-1}};
int ctrl[maxn][maxn];

int main()
{
	int n, m, hx, hy;
	std::cin >> n >> m >> hx >> hy;
	for (int i = 0; i < 9; ++i)
	{
		int tempx = hx + d[i][0], tempy = hy + d[i][1];
		if ((tempx >= 0 && tempx <= n) && (tempy >= 0 && tempy <= m))
		{
			ctrl[tempx][tempy] = 1;
		}
	}
	f[0][0] = 1 - ctrl[0][0];
	for (int i = 0; i <= n; ++i)
	{
		for (int j = 0; j <= m; ++j)
		{
			if(ctrl[i][j]) continue;
			if (i != 0)
				f[i][j] += f[i - 1][j];
			if (j != 0)
				f[i][j] += f[i][j - 1];
		}
	}
	std::cout << f[n][m];
	return 0;
}
